To avoid the possible undesirable effects of volatile vapors entering the atmosphere during a fuel tank filling operation, a number of liquid or fuel systems have been devised. One of such systems, identified broadly as a balanced fuel system, embodies the principle of liquid fuel, and vapor simultaneously flowing between the storage reservoir and a tank being filled. Thus, as liquid is introduced into the fuel tank, vapors comprising both air and fuel vapors are concurrently displaced. The latter are then led back to the storage reservoir or to an alternate vapor holding means.
Since the amount of liquid introduced to the receiving fuel tank is not always equivalent to the amount of vapor which is removed, it is difficult to maintain such a system in a balanced or stabilized condition. More particularly, a number of factors will contribute to the ratio of the vapor to liquid flow which characterizes the condition of the system at any period of time. Such factors include the temperature of the atmosphere about the tank being filled, and the conditions within the reservoir or storage vessel.
To make such a system workable, means is generally provided to avoid an excessive build-up of pressure. Alternately, and to the contrary, it is desirable to avoid the inhalation of excessive amounts of air into the system which would be necessary to achieve the proper system balance.
The intake of any air into the system is of course undesirable since the air mixes with fuel vapors present in the storage reservoir. The combination can, if continued, contribute to a relatively unsafe atmosphere.
While such balanced systems are normally vented to the atmosphere as an expedient toward maintaining their balanced condition, it is found that the amount of air ingested into the system can be minimized. This is possible if the conditions at the nozzle-fuel tank sealed joint can be maintained in such a condition as to avoid the intake of air at the seal face.
Preferably, the pressure at this point in the system is maintained slightly below atmospheric such that in the event the seal is not completely made, the amount of air ingested will be minimal. This will be due to the slight pressure difference between the internal and external conditions about the seal.
In any balanced system that is satisfactory, particularly for widespread commercial use, the instant invention is addressed to the concept of stabilizing the condition at a desired pressure, or vacuum level, immediately adjacent to the nozzle seal. The desired function is achieved primarily through the facility of continuous monitoring of the condition at said point during a liquid transfer operation. Thereafter, the condition is adjusted or maintained within a desired parameter of values. The latter step is achieved by control of the pressure in the seal area through use of a vapor inductor in the vapor evacuation line or conduit.
It is therefore an object of the invention to provide a relatively safe, balanced system adapted to carry a volatile liquid or fuel. A further object is to provide a secondary control system adapted to limit and regulate the amount of air which might enter the system in order to achieve the desired balanced condition. A still further object is to provide a volatile fuel system which is adapted to control the balance of air and fuel vapor transferred during a fueling operation in order to minimize the amount of air which is aspirated into the system by way of the nozzle seal.
While the disclosed system is adapted to handle any form of vaporizable liquid, to illustrate the features of the invention, said liquid will be hereinafter referred to as a liquid fuel such as gasoline or the like.